1. Field of the Invention
The present invention relates to a numerically controlled apparatus capable of automatically and rapidly executing and interrupting working programs, and furthermore restarting these working programs.
2. Description of the Related Art
Various types of numerically controlled apparatus such as numerically controlled milling machines, and numerically controlled grinders have been widely used as machine tools and described in, for instance, Japanese patent publication Nos. 47-3076 (1972), 48-37320 (1973) and No. 53-13838 (1978).
There is shown a block diagram of a conventional numerically controlled apparatus in FIG. 1. A control unit 1 includes a central processing unit (referred to as "CPU"). A memory unit 2 and a calculating unit 3, and a drive controlling unit 4 are connected to the control unit 1. The control unit 1 receives an automatic starting signal 11 transferred from an external controller (not shown). A numerically controlled motor 5 is connected to the drive controlling unit 4.
In response to the automatic starting signal 11, various command data of working programs stored in the memory unit 2 are transferred to the control unit 1. Then, the control unit 1 sends transfer command data to the drive control unit 4 in conjunction with operations of the calculating unit 3. The motor 5 is driven by the drive controlling unit 4 to process a work piece (not shown). When this working operation is interrupted due to various reasons, the tools (not shown) are manually removed to a predetermined shunting position. After solving the causes of the working interruption, these tools are manually returned to the working position where the previous working operation was interrupted. Thereafter, the working programs are manually rearranged to the condition under which the working operation was interrupted. Finally, in response to the automatic starting signal 11, the working operation is again commenced.
Since the conventional numerically controlled apparatus are arranged as illustrated in FIG. 1 and controlled in the above-described manner, the manual operations are necessarily required for shunting the tools from the interruption position to the shunting position, for transferring the tools to the position where the work is again commenced, and for resetting the working program to rearrange the working conditions. A lengthy time period is needed until the working operation is restarted after it was interrupted.
It is therefore an object of the present invention to provide a numerically controlled apparatus for shortening a time period from interruption of the work till re-execution of the work. This is accomplished in such a manner that when the working operation is interrupted, the tools are quickly and precisely shunted from the working position, whereas the tools are rapidly returned to the restarting position when the working operation is again commenced.